Added 28 solutions

2017-03-10 01:10:37 -06:00
parent 3a6797a94a
commit b1992b3e60
37 changed files with 1187 additions and 309 deletions
@@ -0,0 +1,60 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+import java.util.HashMap;
+
+/* Use a HashMap as a cache to speed up runtime 
+ *
+ * Tricky: Must use "long" instead of "int" to avoid integer overflow
+*/
+public class Solution {
+    
+    public static void main(String[] args) {
+        /* Read and save input */
+        Scanner scan = new Scanner(System.in);
+        int n = scan.nextInt();
+        int m = scan.nextInt();
+        int coins[] = new int[m];
+        for (int coins_i = 0; coins_i < m; coins_i++) {
+            coins[coins_i] = scan.nextInt();
+        }
+        scan.close();
+
+        System.out.println(numWays(n, coins));
+    }
+    
+    public static long numWays(int n, int [] coins) {
+        if (n < 0) {
+            return 0;
+        }
+        return numWays(n, coins, 0, new HashMap<String, Long>());
+    }
+    
+    public static long numWays(int n, int [] coins, int coinNumber, HashMap<String, Long> cache) {
+        /* Check our cache */
+        String key = n + "," + coinNumber;
+        if (cache.containsKey(key)) {
+            return cache.get(key);
+        }
+        /* Base case */
+        if (coinNumber == coins.length - 1) {
+            if (n % coins[coinNumber] == 0) {
+                cache.put(key, 1L);
+                return 1;
+            } else {
+                cache.put(key, 0L);
+                return 0;
+            }
+        }
+        /* Recursive case */
+        long ways = 0;
+        for (int i = 0; i <= n; i += coins[coinNumber]) {
+            ways += numWays(n - i, coins, coinNumber + 1, cache);
+        }
+        /* Cache and return solution */
+        cache.put(key, ways);
+        return ways;
+    }
+}